There have been many problems associated with developing rinse aid surface coatings for dishware that provide a beneficial layer with the desirable properties and which minimize the disadvantages, such as a limit to single use protection, insufficient coverage, roughness and/or flaking of coating during use, or in contrast, the inability to remove once applied (when a more temporary coating is desired) and a limit on surfaces that can be modified.
Current approaches to solving the coating problem includes the use of non-dispersive, film-forming polymer coatings and clay-containing, non-dispersive, film-forming polymer coatings. However, the substantivity of the non-dispersive, film-forming polymers (e.g. alkoxylated silicones, poly(N-vinyl-2-pyrrolidones, poly(N-vinyl-imidazoles, diblock copolymers of poly(ethylene oxide) and poly(lactide)) is poor such that its wetting/sheeting effect is short-lived, with spotting/residue negatives returning within 1–2 rinse cycles. Elevating the levels of non-dispersive polymers is not the solution to this problem. This is especially evident on dishware where elevated levels of polymers result in unacceptable residue or film problems. In the case of clay-containing, non-dispersive, film-forming polymer coatings, the nanoparticles are rheology agents for the formulations and do not themselves impart the benefit disclosed.
It is apparent that there is a continuing need to improve the various properties of all dishware surfaces in automatic dishwashers, including but not limited to plastics, metals, glass, wood and stone surfaces, via a dispersive coating composition and method of use which would result in dishware surfaces having one or more of the following highly desirable modified surface properties such as improved wetting and sheeting, uniform drying, anti-spotting, anti-staining, anti-filming, self cleaning, and durability. There is also a continuing need that these modified surface benefits be made the more responsive to consumer applications.
Additional background patents and patent publications, some of which disclose various uses of nanoparticles, include: U.S. Pat. Nos. 4,591,499 and 4,597,886; JP 04-353438; U.S. Pat. No. 5,429,867; JP 96053558; GB 2 303 373; U.S. Pat. No. 5,853,809; PCT WO 99/00457; WO 00/000,554 A1; WO 01/27236; and WO 01/32820.